Minimum feedback radio architecture with digitally configurable adaptive linearization

ABSTRACT

Included is a radio transmission system comprising a plurality of power amplifiers (PAs); a plurality of Volterra Engine (VE) linearizers corresponding to the PAs; a plurality of feedback loops corresponding to the PAs; at least one digital hybrid matrix (DHM) coupled to the VE linearizers; and an analog hybrid matrix (AHM) coupled to the PAs, wherein the feedback loops are connected to the AHM and the VE linearizers but not to the PAs to reduce the number of feedback loops. Also included is a radio system comprising a plurality of PAs; a Volterra DHM (VDHM) coupled to the PAs; a plurality of feedback loops corresponding to the PAs; and an AHM coupled to the PAs, wherein the feedback loops are connected to the AHM but not to the PAs to reduce the number of feedback loops.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/252,065, titled “Minimum Feedback Radio Architecture with DigitallyConfigurable Adaptive Linearization” filed Oct. 15, 2008, whoseinventors are John-Peter van Zelm, and Peter Rashev, which is herebyincorporated by reference in its entirety as if fully and completely setforth herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVENTION

The present invention relates generally to signal amplification andlinearization in radio transmitters and, more particularly, to a systemand method for reducing required signal feedback.

BACKGROUND OF THE INVENTION

In wireless communications, signals are forwarded using radiotransmission and receiving systems. Radio transmission systems mayinclude power amplifiers (PAs), signal linearizers, such as aVolterra-series or Volterra Engine (VE) linearizers, which may becoupled to other system components such as antennas, and signalprocessing components. A digitally configurable radio (DCR), or agileradio, is a type of configurable radio transmission system that supportssmart antenna operation modes, such as Multiple-Input andMultiple-Output (MIMO) or Single-Input and Single-Output (SISO), withouthardware changes or upgrades, for instance using software or firmware.Accordingly, the agile radio can support different signal or beamrelated features, such as power combining, beam forming, sector powerpooling, or combinations thereof.

SUMMARY OF THE INVENTION

In one embodiment, the disclosure includes a radio transmission system.The radio transmission system comprises a plurality of power amplifiers(PAs); a plurality of Volterra Engine (VE) linearizers corresponding tothe PAs; a plurality of feedback loops corresponding to the PAs; atleast one digital hybrid matrix (DHM) coupled to the VE linearizers; andan analog hybrid matrix (AHM) coupled to the PAs, wherein the feedbackloops are connected to the AHM and the VE linearizers but not to the PAsto reduce the number of feedback loops.

In another embodiment, the disclosure includes a radio system. The radiosystem comprises a plurality of PAs; a Volterra DHM (VDHM) coupled tothe PAs; a plurality of feedback loops corresponding to the PAs; and anAHM coupled to the PAs, wherein the feedback loops are connected to theAHM but not to the PAs to reduce the number of feedback loops.

In yet another embodiment, the disclosure includes a multi-port PAsystem. The multi-port PA system comprises a plurality of PAs; aVolterra DHM (VDHM) coupled to the PAs; a plurality of pre-processingblocks corresponding to the PAs; a single feedback loop corresponding tothe PAs; and an AHM coupled to the PAs, wherein the feedback loop isconnected to the AHM, the VDHM, and the pre-processing blocks.

Other aspects and features of the present invention will become apparentto those of ordinary skill in the radio communications art upon reviewof the following description of specific embodiments of the invention inconjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an embodiment of a wireless communicationsystem.

FIG. 2 is a block diagram of an embodiment of a VE based transmissionsystem.

FIG. 3 is a block diagram of an embodiment of a VE based DCR system.

FIG. 4 is a block diagram of an embodiment of a reduced feedback DCRsystem.

FIG. 5 is a block diagram of another embodiment of a reduced feedbackDCR system.

FIG. 6 is a block diagram of another embodiment of a VDHM based DCRsystem.

FIG. 7 is a block diagram of an embodiment of a Peak Power Reduction(PPR) based DCR system.

FIG. 8 is a block diagram of an embodiment of a multi-port PA DCRsystem.

FIG. 9 is a block diagram of another embodiment of a multi-port PA DCRsystem.

FIG. 10 is an illustration of an embodiment of a general-purposecomputer system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It should be understood at the outset that although an exemplaryimplementation of one embodiment of the present disclosure isillustrated below, the present system may be implemented using anynumber of techniques, whether currently known or in existence. Thepresent disclosure should in no way be limited to the exemplaryimplementations, drawings, and techniques illustrated below, includingthe exemplary design and implementation illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

Signal or beam related features of DCRs or agile radios may be supportedusing a plurality of feedback signals associated with a plurality ofpower amplifiers. The feedback signals may be obtained from the poweramplifiers using at least two feedback loops for each power amplifier.Each feedback loop may include a plurality of feedback components, suchas feedback receivers, feedback circuitry, analog to digital converters,etc. Hence, each feedback component in the feedback loop may add to thecost and requirements of the system, such as hardware and softwarecomplexity and maintenance requirements. Further, the feedbackcomponents may increase nonlinear signal combining and cross talkbetween the different feedback loops, which increases errors ordistortions in the transmitted signals and limits signal processingcapacity.

Disclosed herein is a signal transmission system and method using areduced number of feedback loops to decrease nonlinear signal combiningand cross talk, increase signal processing capacity, and reduce systemcost. In an embodiment, the system may comprise a first digitalmultiplexer coupled to a plurality of Volterra Engine (VE) linearizers,a plurality of power amplifiers (PAs) each coupled to a single VElinearizer, and an analog multiplexer coupled to the PAs. To providefeedback to the first digital multiplexer, the system may comprise asingle feedback loop for each pair of VE linearizer and PA, which may becoupled to the analog multiplexer and the first digital multiplexer.Additionally, to provide feedback to the VE linearizers, the system maycomprise a second digital multiplexer, which may be coupled to thesingle feedback loop and the VE linearizers. Alternatively, to providefeedback to the digital multiplexer and the VE linearizers, the systemmay comprise a single digital multiplexer, which may be coupled to theVE linearizers, the PAs, and the single feedback loop. In anotherembodiment, the system may comprise a combined digital multiplexer unit,including a plurality of VE linearizers, a plurality of PAs coupled tothe combined digital multiplexer, an analog multiplexer coupled to thePAs. To provide feedback to the combined digital multiplexer and the VElinearizers within, the system may comprise a feedback loop associatedwith each PA, which may be coupled to the analog multiplexer and thecombined digital multiplexer. Additionally or alternatively, thepresented system architectures may comprise a plurality of multi-portPAs, where each multi-port PA may be associated with a pre-processingcircuit or block and may comprise a plurality of PAs.

FIG. 1 illustrates one embodiment of a wireless communication system 100in accordance with this disclosure. The wireless communication system100 may be a cellular communications network, which may comprise aplurality of base transceiver stations (BTSs) 102 a, 102 b, 102 c and102 d for providing wireless communications to a prescribed coveragearea. Although, four BTSs are shown in the figure, the wirelesscommunication system 100 may comprise any number of BTSs, which may beconfigured similarly or differently. Additionally, the wirelesscommunication system 100 may comprise a Radio Network Controller (RNC)104, which may be coupled to the BTSs 102 a, 102 b, 102 c, and 102 d bymeans of physical or wireless connections. For instance, the BTSs 102 a,102 b, and 102 c may be each coupled to the RNC 104 by a physicalconnection 105, while the BTS 102 d may be coupled to the RNC 104 by awireless connection 106. The wireless communication system 100 may alsocomprise a wireless communication device 130, which may be present orlocated within the prescribed coverage area of the wirelesscommunication system 100. Although, only one wireless communicationdevice 130 is shown in the figure, the wireless communication system 100may also comprise any number of wireless communication devices 130,which may be configured similarly or differently. Accordingly, the RNC104 may be configured to maintain or control wireless communicationsbetween the wireless communication device 130, and the BTSs 102 a, 102b, 102 c, 102 d. Further, the RNC 104 may be coupled to a core network107, which may include a mobile switchgear, a user validation, agateway, or combinations thereof. In turn, the core network 107 may becoupled to other networks, such as a public switched telephone network(PSTN) 108, the Internet 109, at least one other wireless network (notshown), or combinations thereof.

The wireless communication device 130 may wirelessly communicate withany of the BTSs 102 a, 102 b, 102 c, and 102 d depending on its locationor position within the prescribed coverage area. For instance, awireless link established between the wireless communication device 130and the BTS 102 a, 102 b, 102 c, or 102 d may be shifted or “handed off”to another BTS 102 a, 102 b, 102 c, or 102 d, when the mobile terminal130 is moved or repositioned from a proximity of the BTS 102 a, 102 b,102 c, or 102 d to the other BTS 102 a, 102 b, 102 c, or 102 d. Further,the wireless link may conform to any of a plurality oftelecommunications standards or initiatives, such as those described inthe 3rd Generation Partnership Project (3GPP), including Global Systemfor Mobile communications (GSM), General Packet Radio Service(GPRS)/Enhanced Data rates for Global Evolution (EDGE), High SpeedPacket Access (HSPA), Universal Mobile Telecommunications System (UMTS),and Long Term Evolution (LTE). Additionally or alternatively, thewireless link may conform to any of a plurality of standards describedin the 3rd Generation Partnership Project 2 (3GPP2), including InterimStandard 95 (IS-95), Code Division Multiple Access (CDMA) 2000 standards1×RTT or 1×EV-DO. The wireless link may also be compatible with otherstandards, such as those described by the Institute of Electrical andElectronics Engineers (IEEE), or other industry forums, such as theWorldwide Interoperability for Microwave Access (WiMAX) forum.

The BTS 102 a, and similarly any of the BTSs 102 b, 102 c, and 102 d,may comprise a DCR 110, a modem 120, and a communication tower 140. TheDCR 110 and the modem 120 may each be coupled to the communication tower140 and may communicate with one another. The DCR 110 may alsocommunicate with the wireless communication device 130 over an areasubstantially covered by a signal range 150 corresponding to the BTS 102a. The DCR 110 and the wireless communication device 130 may communicateusing a cellular technology standard, such as a Time Division MultipleAccess (TDMA), CDMA, UMTS, or GSM. The DCR 110 and the wirelesscommunication device 130 may communicate using other cellular standards,such as a WiMAX, LTE, or Ultra Mobile Broadband (UMB).

The DCR 110 may be an agile radio head, which may be reconfigured usingsoftware or firmware to extend or reduce the signal range 150, or toincrease the capacity of the wireless communication system 100. Forinstance, the DCR 110 may be reconfigured using a software applicationto communicate with an additional number of wireless communicationdevices 130. The DCR 110 may comprise a plurality of transmitters, aplurality of receivers, or both to support at least one smart antennaoperation mode, such as Multiple-Input and Multiple-Output (MIMO) orSingle-Input and Single-Output (SISO). For instance, the DCR 110 may bereconfigured without hardware changes or upgrades to support signalfeatures comprising power combining, beam forming, sector power pooling,or combinations thereof. Reconfiguring the DCR 110 without hardwarechanges may reduce reconfiguration or upgrade requirements or cost, suchas eliminating or reducing the need for climbing the communication tower140, renting or deploying infrastructure lifting or transfer equipments,or using additional hardware.

The wireless communication device 130 may be any device capable oftransmitting or receiving a signal, such as an analog or digital signal,to and from a radio such as the DCR 110, using a wireless technology.The wireless communication device 130 may be a mobile device configuredto create, send, or receive signals, such as a handset, a personaldigital assistant (PDA), a cell phone (also referred to as a “mobileterminal”), or a wireless-enabled nomadic or roaming device, such as alaptop computer. Further, the wireless communication device 130 may beoptionally configured to provide at least one data service, such as ane-mail service. Alternatively, the wireless communication device 130 maybe a fixed device, such as a base transceiver station or a Femtocell, adesktop computer, or a set top box, which may send or receive data tothe DCR 110.

The communication tower 140 may be any structure on which the DCR 110may be mounted. In other embodiments of the wireless communicationsystem 100, the communication tower 140 may be replaced by a building,other types of towers, e.g. water towers, or other structures suitablefor mounting the DCR 110. Additionally, the communication tower 140 mayconnect the DCR 110 to the modem 120, and as such may providecommunications between the two.

The DCR 110 may comprise a transmitter, such as a baseband transmitterconfigured to implement at least one cellular communications standard,such as CDMA, GSM, UMTS, or WiMAX. The transmitter may comprise a PAthat amplifies a signal before transmission, in addition to a modulationsubsystem, frequency translation subsystem, or combinations thereof. ThePA may be coupled to at least one linearizer configured to compensatefor at least some of the distortions introduced in the signal, e.g.nonlinearities in the PA. The linearizer may be a VE linearizer, such asa VE linearizer disclosed in U.S. Provisional Patent Application Ser.No. 60/788,970 filed Apr. 4, 2006 by Peter Z. Rashev, et al. andentitled “Adaptive Look-Up Based Volterra-series Linearization of SignalTransmitters,” which is incorporated herein by reference as ifreproduced in its entirety. The VE linearizer may be configured toapproximate or implement at least one inverse signal model, using aplurality of Volterra series orders or terms, and hence to compensatefor signal distortion. The inverse signal models may be implementedusing software or firmware. For instance, the inverse signal models maybe executed on a field-programmable gate array (FPGA), applicationspecific integrated circuit (ASIC), digital signal processor,microprocessor, or other types of processors. The inverse signal modelsmay be executed on a computer system, such as a personal computer,server, or other computer system.

FIG. 2 illustrates an embodiment of a VE based transmission system 200,which may be used in radio transmission systems, such as the DCR 110.The VE linearizer 205 may comprise a plurality of multipliers 210, whichmay be coupled to a plurality of real and imaginary dual-port look-uptable (LUT) pairs 220, encapsulated in a “dual-port LUT and multiplier”functional blocks. Accordingly, each multiplier may be coupled to asingle “dual-port LUT and multiplier” functional block. Additionally,each multiplier 210 may be coupled to a tap-delay line 230. Thetap-delay lines 230 may comprise a plurality of delay elements, whichmay be spaced by a spacing of N samples. Specifically, each delayelement (Z^(−n)) may designate a propagation delay of n discretesamples, where n is a discrete time index. Each “dual-port LUT andmultiplier” functional block 220 may be coupled to one of the tap-delaylines 230 via a multiplier implementing a functional mapping f_(i) (i=1,2, 3 . . . ), such as approximating or calculating an input signal orsample delay. The tap-delay line 230 may change a function of a presentinput sample based on future samples. Hence, the tap-delay elements mayform a time axis for the Volterra series, which may comprise a historyof the evolution of a waveform, such as a plurality of polynomialfunctions across time. The outputs of the multipliers 220 and the“dual-port LUT and multiplier” functional block 220 may be addedtogether using a summation block 240 to provide a pre-distorted versionof the digital input sample (x_(n)). The pre-distortion digital inputsample may then be converted to an analog signal, which may beequivalent to the pre-distortion input signal, using a digital-to-analogconverter (DAC) (not shown in the figure). The analog signal may be sentto the amplifier 250, which may be a nonlinear (NL) power amplifier(PA). The analog signal may be up converted to a radio frequency eitherbefore inputting to the amplifier 250. The amplifier 250 may amplify andtransmit the amplified analog signal (y_(n)), for instance using anantenna. The DAC may be coupled to the VE linearizer 205 or theamplifier 250.

Further, a digital feedback signal, which may be a digitized copy of theanalog output or transmitted signal, may be provided to the VElinearizer 205 using an analog-to-digital converter (ADC). Specifically,the amplifier 250 may be coupled to a feedback circuitry 260 comprisinga feedback receiver and any additional component, such as the ADC,configured to forward the digital feedback signal to an adaptivecontroller 270, which may be coupled to the VE linearizer 205 and thefeedback circuitry 260. The analog output of the amplifier 250 may bedown converted from radio frequency to an intermediate frequency or to abaseband frequency before processing by the ADC and/or by the feedbackcircuitry 260. The adaptive controller 270 may be coupled to or comprisean error block 275, which may receive the feedback signal from thefeedback circuitry 260, in addition to a copy of the digital inputsignal of the VE linearizer 205 or a reference signal. In someembodiments, the error block 275 may be coupled to a propagation delaycompensation block (not shown in the figure), which compensates for anydelay in the feedback signal before forwarding the reference signal tothe error block 275 at the adaptive controller 270. Hence, the errorblock 275 may use the digital feedback signal and the reference signalto obtain or calculate an error function, which may then be forwarded tothe VE linearizer 205 and used to obtain the inverse signal processingmodel for pre-distortion compensation. Additionally or alternatively,the adaptive controller 270 may comprise at least one signal processingcircuitry, which uses the feedback and reference signals to obtain acorrection function, which may be forwarded to the VE linearizer 205 andused to obtain the inverse model.

FIG. 3 illustrates an embodiment of a VE based DCR system 300, which maybe used to transmit signals in wireless communication systems, such asthe wireless communication system 100. The VE based DCR system 300 maycomprise a digital hybrid multiplexer (DHM) 310, at least onetransmitter 320, and an analog hybrid multiplexer (AHM) 330. Thetransmitter 320 may be coupled to the DHM 310 and the AHM 330.Additionally, the DHM 310 and the AHM 330 may be coupled to one another.Although, two transmitters 320 are shown in the figure, the VE based DCRsystem 300 may comprise any number of transmitters 320.

The transmitter 320 may comprise a VE linearizer 322 coupled to anonlinear (NL) PA 324, which may be configured similar to the VElinearizer 205 and the amplifier 250, respectively. In some embodiments,the VE linearizer 322 may be a combined VE linearizer, such as a VElinearizer disclosed in U.S. patent application Ser. No. 13/616,159,filed concurrently herewith by John-Peter van Zelm, et al. and entitled“Multi-Dimensional Volterra Series Transmitter Linearization,” which isincorporated herein by reference as if reproduced in its entirety. Assuch, the VE linearizer 322 may comprise a plurality of integrated VElinearizers, which may be arranged in series, in parallel, or both toimprove signal distortion compensation in the system. The VE linearizer322 may forward a combined digital input signal to the corresponding NLPA 324 and may receive, via a feedback loop, a feedback signalequivalent to an amplified analog output signal from the NL PA 324.Accordingly, the VE based DCR system 300 may comprise signal conversioncircuitry (not shown in the figure), such as an ADC, DAC, or both, whichmay be coupled to the VE linearizer 322, the NL PA 324, or both. Thefeedback loop may comprise a feedback circuitry and an adaptivecontroller coupled to the feedback circuitry. The feedback circuitry maybe coupled to the NL PA 324 and may provide a feedback signal from theNL PA 324 to the adaptive controller. The adaptive controller may becoupled to the VE linearizer 322, and may receive a reference signalequivalent to the input signal of the VE linearizer 322 and provide theVE linearizer 322 with a correction or error function. As such, thenumber of feedback loops between the VE linearizer 322 and the NL PA324, or VE feedback loop, maybe equal to the number of transmitters 320.

The DHM 310 may be configured to receive a plurality of digital signals,for instance from a modem, at a plurality of separate input ports, anddivide each digital input signal into a plurality of component signals,which may be substantially similar too one another or to the digitalinput signal. The DHM 310 may distribute the component signals for eachdigital input signal over a plurality of separate output ports, whereeach component signal may be mapped to one output port. As such, eachoutput port may be assigned a plurality of component signals, eachcorresponding to a separate digital input signal. The DHM 310 maycombine the component signals at each output port into a combinedsignal, for instance by summing the component signals. Hence, the DHM310 may forward a substantially similar combined signal from each outputport. In an embodiment, the DHM 310 may be a multiplexer or an N×Ncoupler, where N is an integer representing the number of digital inputsignals that may be combined. For instance, the DHM 310 may receive Ndigital input signals, divide each digital input signal into N componentsignals, combine N component signals from N digital input signals into Ncombined signals, and forward the N combined signals. For example, inthe case where the DHM 310 receives two digital input signals (x₁, x₂),the DHM 310 may forward two combined signals to the transmitter 320, asshown in the figure.

On the other hand, the AHM 330 may be configured to receive a pluralityof analog output signals which may be amplified, from a transmitter 320,at a plurality of input ports. The amplified analog output signals maybe equivalent to amplified versions of the combined signals from the DHM310. The AHM 330 may divide each analog output signal into a pluralityof component signals, which may be equivalent to the inverse of thedistributed component signals at the DHM 310. The AHM 330 may distributeand combine the component signals over a plurality of output ports,similar to the DHM 310, to obtain a plurality of combined signals. Thecombined signals at the AHM 330 may be equivalent to the digital inputsignals of the DHM 310. Accordingly, the AHM 330 may be configured toimplement an inverse process, of distributing and combining signals, ofthe DHM 310. For instance, the DHM 310 may act as a signal multiplexeror coupler, while the AHM 330 may act as the corresponding signalde-multiplexer or de-coupler. However, unlike the DHM 310 that may beconfigured to process digital input signals, the AHM 330 may beconfigured to process analog output signals, which may also be amplifiedand transmitted signals, for instance using an antenna coupled to theAHM 330. In an embodiment, the DHM 310 and the AHM 330 may be hybridmatrix modules, such as the hybrid matrix modules disclosed in U.S. Pat.No. 7,206,355 issued Apr. 17, 2007 by Neil N. McGowan, et al. andentitled “Digitally Convertible Radio,” which is incorporated herein byreference as if reproduced in its entirety.

Using the DHM 310 and the AHM 330, the VE based DCR system 300 mayamplify each input signal partially, and hence amplify each outputsignal sufficiently for transmission. Specifically, each NL PA 324 mayamplify one combined signal from the DHM 310, which may be substantiallysimilar or a copy of the remaining combined signals associated with theremaining NL PAs 324. When one transmitter 320 or one NL PA 324 fails,the remaining combined signals from the DHM 310 may be amplified by theremaining NL PAs 324. The remaining amplified signals may then bereceived and converted or transformed into output signals, which may besufficiently amplified when the number of failed NL PAs 324, and hencethe missing signal power or strength due to the missing combinedsignals, remains tolerable. Additionally, the output signals may besubstantially equivalent to the input signals, and comprise tolerabledistortions or signal degradations due to the missing combined signals.Further, amplifying the combined signals using different NL PAs, mayallow power sharing of the input signals among the NL PAs 324, whereeach combined signal includes different component signals from differentinput signals. As such, additional signal power may be obtained bycombining the outputs of two or more NL PAs 324. Consequently, the VEbased DCR system 300 may comprise lower cost NL PAs 324 with reducedpower or maximum load requirements.

The DHM 310 and the AHM 330 may be coupled to one another, via afeedback loop associated with each transmitter 320. Accordingly, the AHM330 may forward a plurality of feedback signals, each equivalent to atransmitted signal at a transmitter 320, to the DHM 310 via a pluralityof separate feedback loops. The DHM 310 may use each feedback signal,which may also be associated with one digital input signal, tocompensate for signal errors or distortions prior to distributing andcombining the digital input signals. The number of feedback loopsbetween the AHM 330 and the DHM 310, or DCR feedback loop, maybe equalto the number of transmitters 320. Hence, the total number of feedbackloops in the VE based DCR system 300 may be about equal to twice thenumber of VE linearizers 322 or NL PAs 324, which is equal to the sum ofthe number of VE feedback loops and the number of DCR feedback loops.

FIG. 4 illustrates an embodiment of a of a reduced feedback DCR system400 comprising fewer feedback loops than more conventional DCR systems,such as the VE based DCR system 300, and may be associated with aboutthe same number of transmitters. Consequently, the reduced feedback DCRsystem 400 may have higher signal processing capacity with lessnonlinear signal combining and cross talk, which may be introduced by areduced number of feedback components, e.g. feedback circuitry andadaptive controllers. Additionally, due to the reduced number offeedback components, the cost of the reduced feedback DCR system 400 maybe lower than the cost of the more conventional DCR systems.

The reduced feedback DCR system 400 may comprise a first DHM 410, atleast one pair of transmitter components comprising a VE linearizer 422and a corresponding NL PA 424, and an AHM 430, which may be configuredsimilar to the corresponding components of the VE based DCR system 300.However, the reduced feedback DCR system 400 may comprise no VE feedbackloops, i.e. no feedback loops between the VE linearizer 422 and the NLPA 424. Instead, the reduced feedback DCR system 400 may comprise asecond DHM 440 coupled to each VE linearizer 422 and each correspondingDCR feedback loop between the AHM 430 and the first DHM 410.

Specifically, the second DHM 440 may receive a copy of a feedback signalfrom each DCR feedback loop coupled to the AHM 430, and corresponding toa pair of VE linearizer 422 and NL PA 424. The feedback signal may beconverted from analog waveform to digital waveform, for instance usingan ADC or a feedback circuitry, which may be coupled to the DCR feedbackloop. Hence, the second DHM 440 may receive the feedback signal indigital form. The second DHM 440 may be configured similar to the firstDHM 410, and may distribute and combine the feedback signalscorresponding to each VE linearizer 422 and NL PA 424 pair into aplurality of combined feedback signals (X′₁, X′₂). Hence, the second DHM440 may send each combined feedback signal to a corresponding VElinearizer 422. Additionally, each VE linearizer 422 may receive acombined input signal (x′₁, x′₂) from the first DHM 410. The VElinearizer 422 may use the combined feedback signal to correct or adjustfor errors or distortions in the corresponding combined input signal,and hence forward a corrected signal to the NL PA 424.

Using the second DHM 440 in the reduced feedback DCR system 400 mayreplace the need for using a number of VE feedback loops about equal tothe number of VE linearizers 422 in the system. As such, adding onesingle component, i.e. the second DHM 440, in the reduced feedback DCRsystem 400 may be an advantageous compromise, which eliminates the needfor using a greater number of components, including feedback circuitry,adaptive controllers, or other components associated with the feedbackloops. The total number of feedback loops in the system is reduced tothe number of DCR feedback loops, and therefore by about half incomparison to other DCR systems, such as the VE based DCR system 300.

FIG. 5 illustrates an embodiment of another reduced feedback DCR system500, which may comprise a reduced number of feedback loops in comparisonto other DCR systems, without using additional components. The reducedfeedback DCR system 500 may comprise a DHM 510, at least one pair oftransmitter components comprising a VE linearizer 522 and acorresponding NL PA 524, and an AHM 530, which may be configured similarto the corresponding components of the VE based DCR system 300 or thereduced feedback DCR system 500. Similar to the reduced feedback DCRsystem 400, the reduced feedback DCR system 500 may comprise a pluralityof DCR feedback loops, each associated with a pair of VE linearizer 522and NL PA 524, and no VE feedback loops. As such, the total number offeedback loops may be about equal to the number of VE linearizer 522 orNL PA 524.

However, unlike the reduced feedback DCR system 400, the reducedfeedback DCR system 500 may comprise substantially no additionalcomponents in comparison to other conventional DCR systems. Forinstance, the reduced feedback DCR system 500 may not comprise a secondDHM, such as the second DHM 440 of the reduced feedback DCR system 400.Instead, the components of the reduced feedback DCR system 500 may berearranged to provide feedback signals to the VE linearizers 522 and theDHM 510. Accordingly, the DHM 510 may be coupled to the VE linearizers522 and the NL PAs 524, which may be in turn coupled to the AHM 530.Each VE linearizer may receive an input digital signal (x₁, x₂), forinstance from a modem, and forward the signal to the DHM 510. Hence, theDHM 510 may distribute and combine the received signals from the VElinearizers 522, and forward the combined signals to the NL PA 524. Theforwarded combined signals may be digital signals, which may beconverted to analog signals before being received by the NL PA 524, asdescribed above. The NL PAs 524 may amplify and send the signals to theAHM 530, which convert the signals into output signals equivalent to theinput signals and transmit the out output signals.

The AHM 530 may be coupled to each VE linearizer 522 via a DCR feedbackloop to provide the VE linearizers 522 with the corresponding feedbacksignals. The DCR feedback loops may comprise an ADC or similar component(not shown in the figure) to convert the analog signals at the AHM 530to digital signals, which may be processed by the VE linearizers 530.Additionally, the DCR feedback loops may be coupled to the DHM 510, andmay thus provide the DHM 510 with corresponding feedback signals.Accordingly, the AHM 530 may be directly coupled to the VE linearizers522, via the DCR feedback loops, and without an intermediary component,such as the DHM 310 in the case of the VE based DCR system 300 or thesecond DHM 440 in the reduced feedback DCR system 400. Therefore, the VElinearizers 522 may be configured to compensate for nonlinear effects ordistortions, which may be introduced to the feedback signals by the AHM530. Hence, such arrangement of components or DCR architecture may offerimproved signal linearization and quality, in addition to the benefitsof reduced feedback loops.

FIG. 6 illustrates an embodiment of a Volterra DHM (VDHM) based DCRsystem 600, which may comprise an integrated VE based DHM in addition toa reduced number of feedback loops. The VDHM based DCR system 600 maycomprise a Volterra DHM (VDHM) 605, at least one NL PA 624 coupled tothe VDHM 605, and an AHM 630 coupled to the NL PA 624. Additionally, theAHM 630 may be coupled to the VDHM 605 by at least one feedback loop,such that each feedback loop may correspond to one NL PA 624. Hence, thetotal number of feedback loops in the VDHM based DCR system 600 may beabout equal to the number of NL PAs 624. For example, the VDHM based DCRsystem 600 may comprise two NL PAs 624 and two feedback loops, as shownin FIG. 6.

The VDHM 605 may comprise a plurality of sets of VE linearizers 601 anda plurality of couplers 623, which may be each coupled to the sets of VElinearizers 601. The sets of VE linearizers 601 may be each associatedwith one NL PA 624 and coupled to one corresponding feedback loop. Eachset of VE linearizers 601 may comprise at least one VE linearizer 622.For example, each set of VE linearizers 601 may comprise two VElinearizers 622, and hence the total number of VE linearizers 622 in theVDHM 605 may be about twice that of the NL PAs 624 or twice that of thefeedback loops. Each set of VE linearizers 601 may receive a differentinput signal. Each VE linearizer 622 in the set of VE linearizers 601may receive a substantially similar copy of the input signal, processthe signal, and send a substantially similar or different processedsignal to a different coupler 623. The coupler 623 may be configured tocombine the signals received from one VE linearizer 622 in each set ofVE linearizers 601, e.g. VE₁₁ and VE₁₂, or VE₂₁ and VE₂₂, which may besubstantially similar or different signals. The coupler 623 may thenforward the combined signal (x′₁, x′₂) to the corresponding NL PA 624,which may hence be converted from digital waveform to analog waveform.

In turn, the NL PA 624 may forward an amplified analog version of thereceived signal to the AHM 630. The AHM 630 may receive the analogsignals, process the signals, as described above, and transmit aplurality of output analog and amplified signals equivalent to thecorresponding input digital signals. Additionally, the AHM 630 mayforward a plurality of corresponding feedback signals to the VDHM 605.In an embodiment, each set of VE linearizers 601 may be couple to onefeedback loop, and may hence receive one corresponding feedback signal.Each VE linearizer 622 in the set of VE linearizers 601 may receive acopy of the corresponding feedback signal and hence use the feedbacksignal to compensate for signal distortions or linearize the signal.

Since the VDHM 605 may be used to implement both signal linearizationand signal distribution and combining, the VDHM 605 may replace thefunction of a plurality of separate VE linearizers and a DHM. Similar tothe reduced feedback DCR system 500, the VDHM 605 may be directlycoupled to the AHM 630, and hence the individual VE linearizers 622 ofthe VDHM 605 may be configured to compensate for nonlinear or undesiredsignal effects introduced by the AHM 630. In addition to reducing thenumber of feedback loops in the system, using the VDHM 605 may also beadvantageous to further reduce cross talk by substituting parallelarrangements of components, and hence improving system robustness.Finally, the VDHM 605 may allow resource sharing among a plurality ofcomponents, e.g. VE linearizers 622 and couplers 623, which increasessystem efficiency.

FIG. 7 illustrates an embodiment of a peak power reduction (PPR) basedDCR system 700, which may use a VDHM component in PPR base systems. ThePPR based DCR system 700 may be used in wireless or radio systems withstringent signal requirements or low signal degradation tolerance, suchas Orthogonal Frequency-Division Multiplexing (OFDM) based 4G systems.In such systems, PPR techniques may be applied at the modem and beforesignal power amplification to reduce undesired effects introduced by theDHM components in the radio. Specifically, the PPR techniques may beapplied to reduce or limit signal peak to average ratios (PARs), whichmay be further increased due to signal processing at the DHM components.

The PPR based DCR system 700 may comprise modem components, including afirst ideal DHM (iDHM) 701 and at least one PPR block 702 coupled to thefirst iDHM 710. Additionally, the PPR based DCR system 700 may compriseradio components including a delta VDHM (ΔVDHM) 705 coupled to the PPRblock 702, at least one NL PA 724 coupled to the ΔVDHM 705, an AHM 730coupled to the NL PA 724, and a second iDHM 740. The second IDHM 740 maybe coupled, via at least one feedback loop, to the AHM 730 and the ΔVDHM705.

The first iDHM 701 may be configured to distribute and combine the inputsignals, similar to the DHM 410 and the DHM 510. However, unlike the DHMcomponents above, the first iDHM 701 may process the signals in a fixedmanner and may not be reconfigurable. The first iDHM 701 may bepreconfigured to process the input signals based on ideal systemresponse conditions and without receiving or using feedback signals. Forinstance, the first iDHM 701 may be configured in a predetermined mannerbased on an ideal AHM response or feedback signal. Hence, the first iDHM701 may forward each combined signal to a PPR block 702, which may inturn implement at least one PPR technique to control or reduce thesignal power before forwarding the signal to the ΔVDHM 705 in the radio.

The ΔVDHM 705 may be configured to distribute and combine the inputsignals, in an adaptive manner, similar to the DHM 410 and the DHM 510.However, the ΔVDHM 705 may process the signals based on the differencebetween predefined ideal and real system responses and not entirely onreal system responses. Accordingly, the ΔVDHM 705 may process thesignals to compensate from any deviations introduced by the AHM 730 fromits ideal or expected responses. The ΔVDHM 705 may use the feedbacksignals, which may be forwarded from the second iDHM 740 via thefeedback loops, to process the corresponding input signals. The secondiDHM 740 may be configured similar to the first iDHM 701, and may beused in an arrangement similar to the DHM 440 described above tosubstitute for using additional VE feedback loops.

In addition to the compatibility of the PPR based DCR system 700 withstringent signal PAR requirements, the ΔVDHM 705 may add similaradvantages as the VDHM 605, including reducing the number of feedbackloops to about the number of NL PAs 724, compensating for nonlineareffects of the AHM 730, and reducing cross talk.

FIG. 8 illustrates an embodiment of a multi-port PA DCR system 800,which may use a VDHM component and a reduced number of feedback loops.The multi-port PA DCR system 800 may comprise a VDHM 805, at least onemulti-port PA 824 coupled to the VDHM 805, and an AHM 830 coupled to themulti-port PA 824, which may be configured similar to theircorresponding components described above. Additionally, the multi-portPA DCR system 800 may comprise a plurality of pre-processing blocks,each associated with a multi-port PA 824, and a phase shift block 626.Each of the pre-processing blocks may be configured to implementsynchronization, phase alignment, mapping functions, other signalprocessing functions, or combinations thereof.

In an embodiment, the multi-port PA DCR system 800 may comprise twomulti-port PAs 824 and two pre-processing blocks, a main amplifierpre-processing block 802, corresponding to a first multi-port PA 824(PA₁), and a peaking amplifier pre-processing block 804, correspondingto a second multi-port PA 824 (PA₂), as shown in the figure. Further,the two multi-port PAs 824 may comprise a plurality of PAs, which may beconfigured similar to the NL PAs described above. Alternatively, atleast some of the multi-port PAs 824 may be advanced PAs, such asDoherty or Asymmetrical Doherty amplifiers. Each multi-port PA 824 maybe coupled to the AHM 830 and the VDHM 805. Specifically, the firstmulti-port PA 824 (PA₁) may be coupled to one coupler 823 to receive acombined signal from two VE linearizers 822, e.g. VE₁₁ and VE₁₂, whichmay be coupled to the AHM 830, via the feedback loop. On the other hand,the second multi-port PA 824 (PA₂) may receive a phase shifted signalwith respect to the combined signal of the first multi-port PA 824(PA₁). The phase shifted signal may be received by the second multi-portPA 824 (PA₂) via the phase shift block 626, which may be connected tothe input of the first multi-port PA 824 (PA₁). The second multi-port PA824 (PA₂) may also be coupled to another coupler 823 to receive a biassignal from two other VE linearizers 822, e.g. VE₂₁ and VE₂₂. The AHM830 may receive the output signals from the first multi-port PA 824(PA₁) and the second multi-port PA 824 (PA₂), combine the signals into asingle output signal, and transmit the signal, for instance using anantenna. The AHM 830 may also be coupled to the VDHM 805, the mainamplifier pre-processing block 802, and the peaking amplifierpre-processing block 804, via the single feedback loop, and may forwarda feedback signal corresponding to the two multi-port PAs 824accordingly.

In other embodiments, the multi-port PA DCR system 800 may comprise anynumber of multi-port PAs 824 and a corresponding number ofpre-processing blocks and phase shift blocks 626. Accordingly, at leastsome pairs of multi-port PAs 824 may be connected via a phase shiftblock 626 and linked or coupled to two pre-processing blocks and asingle feedback loop, as described above. Hence, the total number offeedback loops in the multi-port PA DCR system 800 may be about equal tohalf the number of multi-port PAs 824.

FIG. 9 illustrates an embodiment of another multi-port PA DCR system900, which may be configured similar to the multi-port PA DCR system800. As such, the multi-port PA DCR system 900 may comprise a VDHM 905,at least one multi-port PA 924 coupled to the VDHM 905, and an AHM 930coupled to the multi-port PA 924. The multi-port PA DCR system 900 mayalso comprise a plurality of pre-processing blocks, for instance a mainamplifier pre-processing block 902 and a peaking amplifierpre-processing block 904, coupled to the VDHM 905 and the AHM 930, via afeedback loop.

However, unlike the multi-port PA DCR system 800, the multi-port PA DCRsystem 900 may not comprise a phase shift block connected or coupled tothe multi-port PAs 924. Instead, each multi-port PA 924 may be coupledto a coupler 923 to receive a combined signal from a plurality of VElinearizer 922 at different sets of VE linearizer 921. For instance, themulti-port PA DCR system 900 may comprise a first multi-port PA 924(PA₁) associated with the main amplifier pre-processing block 902, whichmay receive a combined signal from two VE linearizers 922, e.g. VE₁₁ andVE₁₂. Similarly, the multi-port PA DCR system 900 may comprise a secondmulti-port PA 924 (PA₂) associated with the peaking amplifierpre-processing block 904, which may receive a combined signal from twoother VE linearizers 922, e.g. VE₂₁ and VE₂₂.

At least some of the system components described above, such as acomponent of a VE linearizer, may be implemented on any general-purposenetwork component, such as a computer or network component withsufficient processing power, memory resources, and network throughputcapability to handle the necessary workload placed upon it. FIG. 10illustrates a typical, general-purpose network component 1000 suitablefor implementing one or more embodiments of the components disclosedherein. The network component 1000 includes a processor 1010 (which maybe referred to as a central processor unit or CPU) that is incommunication with memory devices including secondary storage 1020, readonly memory (ROM) 1030, random access memory (RAM) 1040, input/output(I/O) devices 1050, and network connectivity devices 1060. The processor1010 may be implemented as one or more CPU chips, or may be part of oneor more ASICs.

The secondary storage 1020 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 1040 is not large enough tohold all working data. Secondary storage 1020 may be used to storeprograms that are loaded into RAM 1040 when such programs are selectedfor execution. The ROM 1050 is used to store instructions and perhapsdata that are read during program execution. ROM 1050 is a non-volatilememory device that typically has a small memory capacity relative to thelarger memory capacity of secondary storage 1020. The RAM 1040 is usedto store volatile data and perhaps to store instructions. Access to bothROM 1030 and RAM 1040 is typically faster than to secondary storage1020.

Additionally, at least some of the system components described hereinmay be implemented using at least one FPGA and/or ASIC. For instance, atleast some of the system components may be implemented usingpoint-by-point methods in one or more FPGAs, instead of using blockbased methods in a microprocessor. In other embodiments, at least someof the system components may be implemented using an internallyintegrated CPU or an external CPU chip.

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the invention. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of theterm “optionally” with respect to any element of a claim is intended tomean that the subject element is not required. Use of broader terms suchas comprises, includes, having, etc. should be understood to providesupport for narrower terms such as consisting of, consisting essentiallyof, comprised substantially of, etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the preferred embodiments of the present invention.The discussion of a reference in the Description of Related Art is notan admission that it is prior art to the present invention, especiallyany reference that may have a publication date after the priority dateof this application. The disclosures of all patents, patentapplications, and publications cited herein are hereby incorporated byreference, to the extent that they provide exemplary, procedural orother details supplementary to those set forth herein.

What is claimed is:
 1. A radio transmission system comprising: aplurality of power amplifiers (PAs); a plurality of Volterra Engine (VE)linearizers corresponding to the PAs; a plurality of feedback loopscorresponding to the PAs; at least one digital hybrid matrix (DHM)coupled to the VE linearizers; and an analog hybrid matrix (AHM) coupledto the PAs, wherein the feedback loops are connected to the AHM and theVE linearizers but not to the PAs to reduce the number of feedbackloops.
 2. The radio transmission system of claim 1, further comprising:an additional DHM, wherein the additional DHM couples the feedback loopsto the VE linearizers, and wherein the VE linearizers are coupledbetween the DHM and the PAs.
 3. The radio transmission system of claim2, wherein the VE linearizers receive a plurality of combined feedbacksignals from the additional DHM and use the combined feedback signals toadjust a plurality of corresponding combined input signals.
 4. The radiotransmission system of claim 1, wherein the number of feedback loops isabout equal to the number of AHM outputs.
 5. The radio transmissionsystem of claim 1, wherein reducing the number of feedback loopsdecreases nonlinear signal combining and cross talk, increases signalprocessing capacity, reduces system cost, or combinations thereof. 6.The radio transmission system of claim 1, wherein the radio transmissionsystem is an agile radio head.
 7. The radio transmission system of claim6, wherein the radio transmission system is configurable withouthardware changes.
 8. The radio transmission system of claim 6, whereinthe radio transmission system is configurable without hardware changesto support power combining.
 9. The radio transmission system of claim 6,wherein the radio transmission system is configurable without hardwarechanges to support beam forming.
 10. The radio transmission system ofclaim 6, wherein the radio transmission system is configurable withouthardware changes to support sector power pooling.
 11. The radiotransmission system of claim 6, wherein the radio transmission system isconfigurable without hardware changes to support power combining andbeam forming.
 12. The radio transmission system of claim 6, wherein theradio transmission system is configurable without hardware changes tosupport beam forming and sector power pooling.
 13. A radio systemcomprising: a plurality of power amplifiers (PAs); a Volterra digitalhybrid matrix (VDHM) coupled to the PAs; a plurality of feedback loopscorresponding to the PAs; and an analog hybrid matrix (AHM) coupled tothe PAs, wherein the feedback loops are connected to the AHM but not tothe PAs to reduce the number of feedback loops.
 14. The radio system ofclaim 13, wherein the VDHM comprises: a plurality of sets of VolterraEngine (VE) linearizers corresponding to the PAs; and a plurality ofcouplers coupled to the sets of VE linearizers and the PAs, wherein eachset of VE linearizers comprises a plurality of VE linearizers, whereineach coupler connects one VE linearizer from each set of VE linearizersto one corresponding P A, and wherein the feedback loops are connectedto the VDHM.
 15. The radio system of claim 14, wherein each VElinearizer in a set of VE linearizers receives a component signal,substantially similar to an input signal associated with the set of VElinearizers, and wherein the component signals from one VE linearizer ineach set of VE linearizers is combined at the corresponding coupler toobtain a combined signal for each PA.
 16. The radio system of claim 14,wherein each set of VE linearizers is coupled to one correspondingfeedback loop.
 17. A method for performing radio transmission,comprising: receiving one or more input signals at a first digitalhybrid matrix (DHM); providing a first plurality of signals from the DHMto a corresponding plurality of Volterra Engine (VE) linearizers;providing a second plurality of signals from the plurality of VElinearizers to a corresponding plurality of power amplifiers (PAs);providing a third plurality of signals from the plurality of PAs to ananalog hybrid matrix (AHM) coupled to the plurality of PAs; providingfeedback from the AHM to the plurality of VE linearizers, but not to thePAs thereby reducing the number of feedback loops.
 18. The method ofclaim 17, wherein said providing feedback from the AHM to the pluralityof VE linearizers comprises: providing the feedback to a second DHM; andthe DHM providing signals corresponding to the feedback to the pluralityof VE linearizers.
 19. The method of claim 18, wherein the VElinearizers receive a plurality of combined feedback signals from theadditional DHM and use the combined feedback signals to adjust aplurality of corresponding combined input signals.
 20. The method ofclaim 17, wherein the number of feedback loops is about equal to thenumber of AHM outputs.